Photoprocesses of Naphthalene Imide and Diimide Derivatives in Aqueous Solutions of DNA

Abstract

Despite the growing number of redox-active chromophores utilized to photoinduce oligonucleotide cleavage, detailed correlations between the degree of ground-state complexation and product yields have not been developed. To elucidate the specific role of singlet and triplet excited states in nucleotide photooxidation, the photochemical reactivities of N-(2-(N-pyridinium)ethyl)-1,8-naphthalene imide (NI) and N,N‘-bis-[2-(N-pyridinium)ethyl]-1,4,5,8-naphthalene diimide (NDI) with calf-thymus DNA have been explored as a function of ground-state complexation with the DNA polymer. Upon addition of calf-thymus DNA to a phosphate buffered solution of the naphthalene imide derivatives, distinct changes in the UV absorption spectrum of the chromophores, along with single isosbestic points, are observed. Analysis of these changes using the noncooperative model of McGhee and von Hippel yield association constants of (2.46 ± 0.42) × 104 M-1 and (7.78 ± 0.11) × 105 M-1 for NI and NDI, respectively. Pulsed 355 nm excita...